Speaker common wiring
Not a good solution. The active amplifier could damage the one that is off. This could either be an immediate or gradual damage problem. Just add a toggle switch and a IR receiver cover when the TV output is left open circuit.
The output stage of most amplifiers now is class C and as such could be reverse biased under external drive conditions. If the volume is kept very low , you may not experience any problems but as soon as you turn it up too high, *%$#%^&@.
I am a former IC amplifier designer.
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